In the practice of reflectometry, ellipsometry, polarimetry and the like, it is critically important to know the precise angle (AOI), and plane (POI), of incidence at which a beam of electromagnetic radiation is caused to impinge upon a sample, to allow accurate determination of values of sample characterizing parameters, such as the PSI and DELTA thereof. Further, it is noted that the (AOI) and (POI) can change with location on a sample surface as the result of said surface being uneven, thereby requiring alignment at each location of a sample surface investigated. Relative translation between a sample and a reflectometer, ellipsometer or polarimeter can cause an effective sample (AOI) or (POI) orientation change.
Examples of systems which are applicable to effecting sample alignment are disclosed in, patents to Liphardt and Liphardt et al. U.S. Pat. Nos. 7,084,978; 7,230,699; 7,304,792; 7,304,737; and to Johs et al. U.S. Pat. No. 7,277,171. In general, prior art systems provide means for adjusting the orientation of a sample to cause a known, precise angle (AOI) and plane (POI) of incidence.
In view of the above, it should be apparent that a system that reduces the necessity of sample alignment after an initial alignment procedure is performed, would be of benefit and provide utility. In particular, such a system would reduce researcher need to adjust for small changes in (AOI) and (POI) resulting from lateral shifts, or rotation of the a sample, after an initial alignment procedure is performed.